X-LINKED DOMINANT DISORDERS (GROUP 1)
X-linked Dominant Disorders
 Are genetic disorders caused by mutations in genes located on the X
chromosome.
 The mutated gene is dominant, and a person only needs to inherit one copy of the
mutated gene to develop the disorder.
 There is no cure for X-linked dominant disorders, and treatment is generally
focused on managing symptoms and preventing complications. Treatment may
involve a combination of:
 medication
 therapy
 supportive care
 early intervention
 individualized care
Symptoms of X-linked Dominant Disorders
• can vary widely and affect many different parts of the body:
• including developmental delays
• intellectual disability
• neurological problems
• skeletal abnormalities
• skin abnormalities
Diagnosing X-linked Dominant Disorders
 challenging, particularly in males, as they have only one X chromosome.
 Two types of testing:
 Genetic testing - can be used to identify mutations in the responsible genes
 Prenatal testing - is available for families with a known history of X-linked
dominant disorders.
Specific examples of X-linked Dominant Disorders
1. Rett Syndrome - primarily affects girls and causes developmental delays, loss of
motor skills, and problems with communication and coordination
2. Incontinentia Pigmenti - affects the skin, hair, eyes, and teeth and can cause
intellectual disability, seizures, and developmental delays
3. Vitamin D-Resistant Rickets - affects the bones and causes them to become weak
and brittle, leading to skeletal abnormalities and a risk of fractures
Genetic Counseling
 is also important for families affected by X-linked dominant disorders provides
information about the risk of passing the disorder on to future generations and help
families make informed decisions about family planning.
DISORDERS WITH MULTIFACTORIAL INHERITANCE (GROUP 2)
Multifactorial Inheritance
 Also known as complex or polygenic inheritance refers to the genetic
predisposition to a particular disease, which is influenced by multiple genetic and
environmental factors.
Examples of Multifactorial Inheritance:
1. Cardiovascular Diseases
 Hypertension, coronary artery disease, and stroke, are among the most common
diseases with multifactorial inheritance. Several genetic and environmental factors,
such as obesity, smoking, and high blood pressure, contribute to the development
of these diseases.
2. Diabetes
 Type 2 diabetes is another disease with multifactorial inheritance. Genetic factors,
such as family history, and environmental factors, such as obesity and physical
inactivity, can increase the risk of developing diabetes. A complex interplay
between these factors can lead to insulin resistance and high blood sugar levels.
3. Cancer
 Many types of cancer have a multifactorial inheritance pattern. Genetic mutations,
such as those in BRCA1 and BRCA2 genes, can increase the risk of developing
breast, ovarian, and other cancers. Environmental factors, such as exposure to
radiation and carcinogenic chemicals, also play a significant role in the
development of cancer.
4. Autoimmune Diseases
 Autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, and lupus,
are also diseases with multifactorial inheritance. Genetic and environmental
factors can trigger an autoimmune response, leading to the destruction of healthy
tissues and organs.
5. Mental Health Disorders
 Mental health disorders, including depression, anxiety, and bipolar disorder, have
a multifactorial inheritance pattern. Genetic factors, such as family history, and
environmental factors, such as stress and trauma, can increase the risk of
developing these disorders.
CYTOGENETIC DISORDERS (GROUP 3)
Cytogenetic Disorders
 An abnormality in the number or structure of chromosomes, typically manifested
as a gain (duplication), loss (deletion), exchange (translocation), or sequence
change (inversion) of genetic material.
 Can occur from numeric or structural abnormalites of chromosomes.
 Can affect sex chromosomes to autosomes.
Numeric Abnormalities
 A type of chromosome abnormality. These types of birth defects occur when there
is a different number of chromosomes in the cells of the body from what isusually
found.
 Euploid State: When the number of chromosomes is normal (46, or 23 pairs).
Polypoidy
 Polypoidy is the possession of more than two sets of homologous chromosomes.
Aneuploidy
 Aneuploidy is any chromosomal number that is not an exact multiple of a haploid
number. Ex: 47 chromosomes
 The most common cause of Aneuploidy is the nondisjunction of either a pair of
homologous chromosomes during meiosis 1 or failure of sister chromatids during
meiosis 2. This will result in the gamete having one extra or one less chromosome.
Mosaicism
 Mosaicism occurs when a person has two or more genetically different sets of
cells in his or her body. If those abnormal cells begin to outnumber the normal
cells, it can lead to disease that can be traced from the cellular level to affected
tissue, like skin, the brain, or other organs.
 It is caused by an error in cell division very early in the development of the unborn
baby.
Examples of Mosaicism
1. Mosaic Down Syndrome
 Diagnosed when there is a mixture of two types of cells. Some have the usual 46
chromosomes, and some have 47. Those cells with 47 chromosomes have an
extra chromosome 21.
2. Klinefelter Syndrome
 KS Mosaicism 46, XX/47, XXY is an extremely rare disorder of sex development
characterized by the presence of both ovarian and testicular tissues in the same
individual.
3. Mosaic Turner Syndrome
 Turner Syndrome is a condition in which cells inside the same person have
different chromosome packages. Mosaic TS can affect any cell in the body. Some
cells have X chromosomes and some don't. Every 3 out of every 10 girls with TS
will have some form of Mosaic TS
Structural Abnormalities
 Usually results from chromosomal breakage, resulting in loss or rearrangement of
genetic material.
Patterns of Breakage
1. Translocation
 When a segment of one chromosome separates and attaches to another
chromosome, the condition is known as translocation
 Two kinds of translocation:
 Robertsonian translocation
 In a Robertsonian translocation, the short arms of a single, fused
chromosome are left behind when the long arms of two non-homologous
chromosomes link together. People with Down syndrome frequently
experience this kind of translocation.
 Reciprocal translocation
 A genetic rearrangement occurs when two non-homologous chromosomes
exchange parts with one another. This may have no apparent effects on the
person, or it may cause cancer or developmental issues.
2. Inversion
 A chromosomal inversion happens when a section breaks off and reattaches
within the same chromosome, but in the opposite orientation. DNA may or may not
be lost as a result of the process.
 Two types of inversion:
1. Paracentric Inversion
 Inverted segment on the short/long arm.
2. Pericentric Inversion
 Breaks occur on both the short/long arm.
3. Deletion
 A deletion is a type of chromosomal abnormality that occurs when a part of a
chromosome is missing or deleted. Deletions can range in size from small (a few
base pairs) to large (several megabases), and can occur spontaneously or as a
result of exposure to certain environmental factors.
4. Isochromosomes
 Isochromosomes are chromosomes that have two identical arms because they
split incorrectly during cell division. This results in a chromosome with two identical
long arms or two identical short arms.
 Isochromosomes can cause a variety of genetic disorders, including Turner
syndrome and Pallister-Killian syndrome.
 Isochromosomes can occur in any chromosome, but are most commonly found in
sex chromosomes (X and Y).
5. Ring Chromosomes
 are typically found in chromosomes 13, 14, or 15, but can occur in any
chromosome.
 occur when a chromosome breaks in two places and the ends fuse together,
forming a ring shape. This can result in the loss of genetic material from the
chromosome, leading to various symptoms depending on which genes are
affected.
 can cause developmental delays, intellectual disability, and growth abnormalities,
among other symptoms.
General Features of Cytogenetic Disorders
 Linked to chromosome lack, excess, or aberrant rearrangements.
 Genetic material loss causes more severe problems than genetic material gain.
 Sex chromosomal abnormalities were often accepted better than autosome
abnormalities.
 Sex chromosomal abnormalities are frequently undetectable at birth.
 The majority of cases are the result of new alterations.
CYTOGENETIC DISORDERS INVOLVING AUTOSOMES (GROUP 4)
Trisomy 21 (Down Syndrome)
 The most common human chromosomal anomaly.
 The disorder was named after John Langdon Down, a British physician who first
identified it in 1866.
 A genetic disorder in which a person has 3 copies of their 21st chromosome in
every cell in their body.
 They may be born with intellectual disabilities and congenital malformations (birth
defects).
 While there is no cure for Down Syndrome, there are support and special
educational programs available to assist individuals and their families.
Down Syndrome (Trisomy 21) may result to health issues such as:
 Congenital Heart Disease
 Duodenal Atresia
 Congenital Hypothyroidism
 Hearing loss and otitis media
 Epilepsy
Common characteristics and facial features of Trisomy 21 (Signs and Symptoms):
 flattened face especially in the bridge of the nose
 almond shaped eyes that slant up
 short and thicker neck
 tongue that tends to stick out of the mouth
 tiny white spots on the iris of the eye
 small ears, hands, and sandal toe feet
 poor muscle tone
 shorter in height
 thin hair
Diagnosis of Trisomy 21
 Early diagnosis allows for appropriate interventions and support services to be put
in place, which can significantly improve the quality of life for individuals with Down
syndrome and their families.
 Two ways: Prenatally and Postnatally
 Prenatal Diagnosis
 Prenatal Screening Tests - hese tests estimate the risk of the fetus having
Down syndrome but do not provide a definitive diagnosis. One example is
noninvasive prenatal testing (NIPT), which analyzes cell-free fetal DNA in the
mother's blood.
 Prenatal Diagnostic Tests - These tests provide a definitive diagnosis by
analyzing the chromosomes of the fetus. They are invasive and carry a small
risk of miscarriage. Examples include chorionic villus sampling (CVS),
typically performed between 10 and 13 weeks of pregnancy, and
amniocentesis, performed between 15 and 20 weeks of pregnancy.

Postnatal Diagnosis:
 Physical Examination - A newborn suspected of having Down syndrome
based on their physical features may undergo further testing to confirm the
diagnosis.
 Chromosomal Analysis - The most definitive way to diagnose Down
syndrome postnatally is through a chromosomal analysis called a karyotype.
This test involves taking a blood sample and examining the chromosomes
under a microscope to identify the presence of an extra chromosome 21.
Causes of Trisomy 21
 Down syndrome is usually caused by an error in abnormal cell division called
“nondisjunction” during the formation of the sperm or egg.
 Instead of having the usual 46 chromosomes (23 pairs) in their cells, individuals
with Down syndrome have 47 chromosomes, with an extra copy of chromosome
21 due to nondisjunction.
 During the formation of sperm or egg cells (a process called meiosis), irregularities
may occur, leading to the presence of an extra chromosome 21. Consequently,
when the sperm fertilizes the egg, the resulting zygote has 47 chromosomes
instead of the standard 46.
Three types of chromosomal changes that can lead to Down syndrome:
1. Complete trisomy 21 - An error during the formation of the egg or the sperm results
in either one having an extra chromosome.
2. Mosaic trisomy 21 - Occur when the error in cell division takes place early in
development but after a normal egg and sperm unite.
3. Translocation trisomy 21 - The extra part of the chromosome gets "stuck" to
another chromosome and gets transmitted into other cells as the cells divide, and this
type of change causes a small number of Down syndrome cases.
Trisomy 18 (Edwards Syndrome)
 John Hilton Edwards, et al.., discovered Edwards Syndrome in 1960 after
researching a newborn with multiple congenital complications and issues with
cognitive development.
 A chromosomal condition associated with abnormalities in many parts of the body
 A chromosome disorder characterized by having 3 copies of chromosome 18
instead of the usual 2 copies.
 Can result in a live birth, but Trisomy 18 most often causes a miscarriage during
the first three months of pregnancy or the baby is stillborn
 Many babies with Trisomy 18 do not survive past the first few months of life due to
the severity of their health problems
 If a parent had a child with Edwards Syndrome (Trisomy 18) and becomes
pregnant again, it’s unlikely they’ll have another child diagnosed with the same
condition (no more than 1%).
 Occurs in an estimated 1 out of every 5,000 to 6,000 live births.
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The condition Is more common during pregnancy (1 out of 2,500 pregnancies),
but most (at least 95%) fetuses don’t survive full term due to complications from
the diagnosis
Pregnancies can end in miscarriage or babies are stillborn
Issues relating to the heart affect nearly 90% of children diagnosed with Edwards
syndrome (trisomy 18) and are the leading cause of premature death among
infants who have the condition, next to respiratory failure.
Signs and symptoms of Trisomy 18
 Poor growth before and after birth
 multiple birth defects
 severe developmental delays or learning problems
 Severe intellectual disability
 Low birth weight
 A small abnormally shaped head
 A small jaw and mouth
 Clenched fists with overlapping fingers
 Congenital heart defects
 Various abnormalities of other organs
 Most cases are not inherited and occur sporadically (by chance)
 Symptoms may start to appear during pregnancy and as a newborn
Causes of Trisomy 18
 Changes in the way information is arranged into chromosome
 The presence of an extra copy of chromosome 18, which results from a random
error in cell division during the formation of the egg or sperm, or during early fetal
development.
 Is not typically caused by an inherited genetic mutation or a specific environmental
factor, and is usually a random event
 In rare cases, it can be caused by a translocation, in which a piece of chromosome
18 breaks off and attaches to another chromosome
 the likelihood that a parent will have a child with Edwards syndrome (Trisomy 18)
increases with maternal age at the time of pregnancy.
Trisomy 13 (Patau Syndrome)
 is a rare genetic condition when an extra copy of chromosome 13 attaches to a
pair of chromosomes.
 is caused by nondisjunction of chromosomes during meiosis (the mosaic form is
caused by nondisjunction during mitosis). Like all nondisjunction conditions (such
as Down syndrome and Edwards syndrome), the risk of this syndrome in the
offspring increases with maternal age at pregnancy, with about 31 years being the
average.
Symptoms of Trisomy 13
 Trisomy 13 affects how the face, brain, and heart develop, along with several other
internal organs. They are life-threatening and many cases result in a miscarriage
or the baby passing away before turning one year old (script opening for
symptoms here)
 Very small or poorly developed eyes (microphthalmia)
 Extra fingers or toes
 An opening in the lip with or without an opening in the roof of the mouth
 weak muscle tone (hypotonia)
 Heart abnormalities present at birth (congenital)
 Physical growth irregularities with many cases targeting the spinal cord
 Severe issues with cognitive function
 Underdeveloped internal organs
Causes of Trisomy 13
 There are three possible ways for a trisomy to form at chromosome 13:
1. Complete trisomy 13 - Random copying errors where more genetic material
connects to a chromosome than necessary (complete trisomy 13) during the
formation of the sperm and egg before conception causes trisomy 13. People
with trisomy 13 have three copies of chromosome 13 instead of two. The extra
genetic material attached to chromosome 13 causes symptoms of the condition.
2. Translocation - In about 20% of trisomy 13 cases, symptoms occur when part of
chromosome 13 attaches to a nearby chromosome when eggs and sperm form
(translocation) during fetal development. In this case, there are two pairs of
chromosome 13, and an additional copy of chromosome 13 forms and bonds
with a nearby chromosome pair, not necessarily in the 13th position.
3. Mosaic trisomy 13 - In rare cases, an extra copy of chromosome 13 appears in
some cells in the body but not all cells. This means that some cells in the body
have three chromosome 13’s and others only have a pair of chromosome 13
(euploid). The severity of symptoms for a mosaic trisomy 13 diagnosis depends
on how many cells have the third copy of trisomy 13. Symptoms are more severe
if more cells have a third copy.
CYTOGENETIC DISORDERS INVOLVING SEX CHROMOSOMES (GROUP 5)
Cytogenetic Disorder
 Irregularity in the number or structure of chromosomes.
 Usually in the form of a gain (duplication), loss (deletion), exchange
(translocation), or alteration in sequence (inversion) of genetic material.
 Genetic conditions caused by damage, addition, or loss of sex chromosomes are
known as sex chromosome abnormalities.
 According to statistics, 1 in 400 males and 1 in 650 females show some form of
sex chromosome abnormality.
Types of Cytogenetic Disorders Involving Sex Chromosomes
 Klinefelter Syndrome
 Chapelle Syndrome
 Jacobs Syndrome
 Triple X syndrome
 Swyer Syndrome
 Turner Syndrome
 True Hermaphroditism
Klinefelter Syndrome (XXY Syndrome)
 Occurs in 1 out of 650 births
 Caused by having an extra X chromosome in males
 Males with Klinefelter syndrome tend to acquire female attributes: breast
development, absence of chest hair and beard, narrow shoulders, wide hips, etc.
Chapelle Syndrome (XX Syndrome)
 Occurs in 1 out of 20,000 births; a rare genetic disorder.
 Affected people have two X chromosomes (the pair usually found in females), but
possess male external genitalia.
 Children with XX Male syndrome are usually raised with a male gender identity.
Jacobs Syndrome (XYY Syndrome)
 Found in 1 out of 1,000 males
 Caused by an extra Y chromosome from the father
 People with this condition are usually taller but may develop learning disabilities or
behavioral problems
Triple X/Trisomy X Syndrome, 47 XXX (XXX Syndrome)
 Occurs in about 1 out of every 1,000 female births; a rare condition in women
 The chances of these errors rise as a mother ages.
Symptoms
 Clinodactyly of the 5th finger - Permanent curving of the pinkie finger
 Cognitive impairment - Deficits in thinking, reasoning, or remembering
 Epicanthus - Prominent eye folds
 Tall stature
 Specific learning disability - Impairment of certain skills such as reading or writing,
coordination, self-control, or attention that interfere with the ability to learn
Swyer Syndrome (XY Syndrome)
 Rare disorder characterized by the failure of the sex glands (i.e., testicles or
ovaries) to develop.
 Females with this syndrome have an XY chromosomal makeup instead of an XX
chromosomal makeup.
 Females with Swyer Syndrome have “gonadal streaks”, in which the ovaries do
not develop properly (aplasia) and are replaced by functionless scar (fibrous)
tissue.
 Caused by mutations of genes that are involved in the sex development of a fetus
with an XY chromosomal makeup.
 Symptoms
 Relatively tall, small uterus, slightly enlarged clitoris compared to most women
 They do not experience any outward symptoms until their early teens when they
fail to begin having a period (primary amenorrhea)
 Development of gonad tumors
 Streak Gonads - functionless connective tissue that does not secrete sex
hormones
Turner/Monosomy Syndrome, 45 X (X Syndrome)
 Affects about 1 in every 2,000 to 2,500 girls
 Occurs when part or all of an X chromosome is missing from most or all of the
cells in a girl's body
 Some treatments can help minimize its symptoms, such as human growth
hormone
Symptoms
 Underdeveloped breasts and widely-spaced nipples
 Underdeveloped ovaries
 Short stature
 Webbed neck
 Elbow deformity
 Low hairline
 Constricted aorta
 Short arms and legs
 Absence of menstruation
Mixed Gonadal Dysgenesis (MGD)
 Incidence of this rare disease is less than 1 per 15,000 births
 Rare intersexual disorder that is often defined by the presence of a testis on one
side of the body and a streak gonad on the other side.
 Streak gonad may be imperfectly developed and not have matured into an ovary
or a testis.
 May develop features typical of a girl, a boy, or both a girl and a boy.
Pure Gonadal Dysgenesis (PGD)
 Found in 1 in 80,000 to 1 in 100,000 people
 Defined as the complete or near complete absence of ovarian tissue in females
and the development of streak gonads (underdeveloped ovaries)
 Females with PGD have normal genitalia and continuous development of their
uterus and fallopian tubes in childhood; however during adulthood due to their
streak gonads, they experience sexual infantilism
True Hermaphroditism (XX XY Ovotesticular Syndrome)
 Intersex condition in which an individual is born with both ovarian and testicular
tissue
 Can be caused by the division of one ovum (egg cell), followed by fertilization of
each haploid ovum and fusion of the two zygotes early in development
 Alternately, an ovum can be fertilized by two sperm followed by trisomic rescue
(condition characterized by an additional chromosome, e.g. down syndrome) in
one or more daughter cells
 It can be associated with a mutation in the SRY gene
SRY Gene
 Believed to be critical in initiating male sex determination by triggering
undifferentiated gonadal tissue to transform into testes
 Y chromosome contains a "male-determining gene," that causes testes to form in
the embryo and results in the development of external and internal male genitalia
 Suggests that the condition is the result of the constitutive activation of a gene
normally triggered by SRY
KLINEFELTER'S SYNDROME AND TURNER SYNDROME (GROUP 6)
Klinefelter Syndrome
 One of the hereditary diseases that affects men
 An extra X chromosome is typically present at birth in males due to a hereditary
abnormality.
 one in a thousand males have it
 The unwanted extra sex chromosome is the outcome of a chance mistake during
the development of the egg or the sperm. It is distinguished by the presence of 47
chromosomes overall rather than 46 because of an additional copy of the X
chromosome
 Males who have Klinefelter syndrome may have trouble paying attention, writing,
narrating, and spelling. They could have a tendency to be more introverted, timid,
and shy than other men
 Some Klinefelter syndrome boys have a diminished interest in sports or physical
activity.
Symptoms of Klinefelter
 Signs and symptoms of Klinefelter syndrome vary widely among males with the
disorder. Many boys with Klinefelter syndrome show few or only mild signs.
 The condition may go undiagnosed until adulthood, or it may never be diagnosed.
For others, the condition has a noticeable effect on growth or appearance. Signs
and symptoms of Klinefelter syndrome also vary by age.
Symptoms in Babies
 Weak muscles
 Slow motor development taking longer than average to sit up, crawl, and walk
 Delay in speaking
 Problems at birth, such as testicles that haven't descended into the scrotum
Boys & Teenagers Symptoms
 Taller than average stature
 Longer legs, shorter torso, and broader hips compared with other boys
 Absent, delayed or incomplete puberty
 After puberty, less muscle and less facial and body hair compared with other teens
 Small, firm testicles
 Small penis
 Enlarged breast tissue (gynecomastia)
 Weak bones
 Low energy levels
 Tendency to be shy and sensitive
 Difficulty expressing thoughts and feelings or socializing
 Problems with reading, writing, spelling, or math
Men Symptoms
 Low sperm count or no sperm
 Small testicles and penis
 Low sex drives
 Taller than average height
 Weak bones
 Decreased facial and body hair
 Less muscular compared with other men
 Enlarged breast tissue
 Increased belly fat
Causes of Klinefelter
 Klinefelter syndrome occurs as a result of a random error that causes a male to be
born with an extra sex chromosome.
 It isn't an inherited condition.
 Humans have 46 chromosomes, including two sex chromosomes that determine a
person's sex.
 Females have two X sex chromosomes (XX).
 Males have an X and a Y sex chromosome (XY).
 One extra copy of the X chromosome in each cell (XXY), the most common cause
 An extra X chromosome in some of the cells (mosaic Klinefelter syndrome), with
fewer symptoms
 More than one extra copy of the X chromosome, which is rare and results in a
severe form. Extra copies of genes on the X chromosome can interfere with male
sexual development and fertility.
Klinefelter Diagnosis
 The main tests used to diagnose Klinefelter syndrome are:
1. Hormone testing
 Blood or urine samples can reveal abnormal hormone levels that are a sign of
Klinefelter syndrome.
2. Chromosome analysis (Karyotype Analysis)
 This test is used to confirm a diagnosis of Klinefelter syndrome. A blood
sample is sent to the lab to check the shape and number of chromosomes. A
small percentage of males with Klinefelter syndrome are diagnosed before
birth. The syndrome might be identified in pregnancy during a procedure to
examine fetal cells drawn from the amniotic fluid (amniocentesis) or placenta
for another reason — such as being older than age 35 or having a family
history of genetic conditions.
 Klinefelter syndrome may be suspected during a noninvasive prenatal screening
blood test. To confirm the diagnosis, further invasive prenatal testing such as
amniocentesis is required.
Klinefelter Treatment
 Klinefelter syndrome has no cure, but some of the symptoms associated with the
condition can be treated if necessary.
 Testosterone replacement therapy (TRT) - is one of the treatments given to
males with testosterone disorder to treat hypogonadism or low testosterone levels.
 For children, it can be taken in the form of gels or tablets, or given as gel or
injections in adult men.
Klinefelter Prevention
 Klinefelter syndrome is a genetic disorder that unfortunately cannot be avoided.
 It is an unavoidable genetic error that develops prior to birth.
 There is nothing a parent can do to stop their child from developing Klinefelter
syndrome because the condition is not inherited (not handed down through the
family).
Turner Syndrome
• Turner Syndrome is a disorder that primarily affects females and is brought on by
a missing or partially missing X chromosome (also known as the sex
chromosomes).
• Short stature, failure of the ovaries to mature, and heart anomalies are just a few
of the medical and developmental issues that Turner syndrome can bring on. It is
a hereditary condition that is occasionally referred to as congenital ovarian
hypoplasia syndrome.
• A person is born with Turner syndrome since it is a congenital disorder. As every
one of us is born with two chromosomes, an absence of one or both of the X
chromosomes is known as chromosomal abnormally.
Symptoms
• Almost all girls with Turner Syndrome will grow up to be shorter than average, with
underdeveloped ovaries.
• Girls with Turner syndrome also have distinctive features and associated health
conditions, some of which may be apparent from birth. They may be born with
swollen hands and feet, caused by a build-up of excess fluid (lymphoedema) in the
surrounding tissues, but this usually clears soon after birth.
Other features that may have developed in the womb include:
• Thick neck tissue
• Swelling of the neck (cystic hygroma)
• Being small baby
• Heart conditions
• Kidney abnormalities
Growth
• Babies with Turner syndrome may grow at a normal rate until they’re 3 years old.
After this, their growth slows down. At puberty, usually between 8 and 14 years, a
girl with Turner syndrome will not have the normal growth spurt, even with female
oestestrogenmone replacement therapy (HRT).
• Girls with Turner syndrome are typically short in relation to the height of their
parents. On average, adult women with untreated Turner syndrome are 20cm
shorter than adult women without the syndrome.
• Treatment with additional high-dose growth hormone hormone reduces this
difference by about 5cm (about 2in) on average.
Ovaries
• During puberty, a girl’s ovaries usually begin to produce the sex hormones,
oestrogen, and once fully mature, progesterone. These trigger periods to begin.
• Most girls with Turner syndrome do not produce enough of these sex hormones,
which means:
• They may not begin sexual development or fully develop breasts without
female hormone replacement therapy (HRT)
• They may begin sexual development but not complete it.
• They may not start their monthly periods naturally.
• It’s likely they’ll be need help to have a baby.
General Features
• a particularly short, wide neck (webbed neck)
• a broad chest and widely spaced nipples
• arms that turn out slightly at the elbows
• a low hairline
• teeth problems
• a large number of moles
• small, spoon-shaped nails
• a short 4th finger or toe Eyes
• eyes that slant downwards
• droopy eyelids (ptosis)
• a squint (strabismus)
• lazy eye (amblyopia)
• cataracts – cloudy patches in the lens at the front of the eye
• short-sightedness (myopia) Ears
• low-set ears
• recurring middle ear infections (otitis media) and glue ear during early childhood
• hearing loss – this can occur in later life but is often more severe and develops
earlier than the normal age-related decline in hearing
Causes
• Turner syndrome occurs when part or all of an X chromosome is missing from
most or all of the cells in a girl’s body. A girl normally receives one X chromosome
from each parent. The error that leads to the missing chromosome appears to
happen during the formation of the egg or sperm.
• Most commonly, a girl with Turner syndrome has only one X chromosome.
Occasionally, she may have a partial second X chromosome. Because she is
missing part or all of a chromosome, certain genes are missing. The loss of these
genes leads to the symptoms of Turner syndrome.
Turner Syndrome Diagnosis
 Turner syndrome is usually identified during childhood or at puberty. However, it
can sometimes be diagnosed before a baby is born using a test called
amniocentesis.
 Pregnancy and birth Turner syndrome may be suspected in pregnancy during a
routine ultrasound scan if, for example, problems with the heart or kidney are
detected.
 Lymphoedema, a condition that causes swelling in the body's tissues, can affect
unborn babies with Turner syndrome, and may be visible on an ultrasound scan.
 Turner syndrome is sometimes diagnosed at birth as the result of heart problems,
kidney problems or lymphoedema.
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Childhood
 If a girl has the typical characteristics and symptoms of Turner syndrome,
such asshort stature, a webbed neck, a broad chest and widely spaced
nipples, the syndrome may be suspected. It's often identified during early
childhood, when a slow growth rate and other common features become
noticeable.
In some cases, a diagnosis is not made until puberty when breasts do not develop
or monthly periods do not start.
Girls with Turner syndrome are typically short in relation to the height of their
parents. But an affected girl who has tall parents may be taller than some of her
peers and is less likely to be identified based on her poor growth.
Karyotyping
 Karyotyping is a test that involves analysing the 23 pairs of chromosomes. It's
often used when Turner syndrome is suspected. The test can either be
carried out while the baby is inside the womb – by taking a sample of amniotic
fluid (amniocentesis) – or after birth by taking a sample of the baby's blood.
Turner Syndrome Treatment
• Turner syndrome has no cure, but some treatments can help minimize its
symptoms. Some of the treatments include:
1. Growth hormone therapy
• Girls with Turner syndrome are entitled to receive high-dose growth
hormone therapy as soon as it becomes apparent that they're not growing
normally. Growth hormone therapy given in early childhood will help to
increase the Child's growth.
2. Estrogen and progesterone replacement therapy
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Estrogen Therapy - triggers changes usually during puberty, such as
breast development. It can be given as a gel, tablet, or patch.
Progesterone therapy - will cause monthly periods to start
Turner Syndrome Prevention
• Turner syndrome is unavoidable. It is a genetic condition brought on by an
unintentional error that results in a missing X chromosome in a parent's sperm or
egg.
• The mother and father are unable to stop this error from happening. However, as
previously mentioned, there are numerous options for therapy.